PHOENIX -- In 1994, when first running for Congress, J.D. Hayworth, who today is 51 and trying to wrest from John McCain, 73, the Arizona Republican Party's Senate nomination, went jogging in Washington wearing a T-shirt given to him by some Arizona loggers. Federal solicitude for the supposedly endangered spotted owl was bedeviling the timber industry, and Hayworth's shirt read: "If two teenagers can procreate in the back seat of a Volkswagen, why does a spotted owl need 2,000 acres?" Hayworth's jog intersected President Clinton's, so Hayworth subsequently told the loggers he had "run your message past the president." Hayworth's middle name is not Nuance.

Washed into Washington by the 1994 Republican wave, he was washed out in 2006 by a Democratic wave. Born in North Carolina, he is a burly ex-football player for North Carolina State. Having been a television sportscaster here before entering politics, Hayworth bounced from defeat to a talk radio station. There he put his flair for rhetorical fireworks in the service of his favorite causes, two of which are stopping illegal immigration and deploring the insufficiencies of McCain's conservatism. Those insufficiencies include, Hayworth says, opposition to the Bush tax cuts, and support for bailouts and for what Hayworth characterizes as "amnesty" for illegal immigrants.

McCain, who has a flair for umbrage, felt some about another Hayworth cause -- a possible Hayworth Senate candidacy. So McCain, whose pugnacity is part of his charm, for those who are charmed, went after Hayworth with tactics that reminded other people why they are not charmed. The co-author of the McCain-Feingold restrictions on political speech asked the Federal Election Commission to silence Hayworth.

Although Hayworth was not yet a candidate, McCain argued that he was receiving from the station's owner an illegal "corporate in-kind contribution" of "as much as" $540,000 a week, a figure concocted by pricing Hayworth's 15 hours per week at the rate advertisers would pay for 1,800 30-second spots. Hayworth spared his station the litigation costs by becoming a candidate.

Hayworth and McCain, who is seeking a fifth term, will gnaw on each other until the August primary, the rules of which are still unclear. Usually, primary turnouts are low, but this shootout will be unusually enticing. Republican primaries have been open to unaffiliated voters, but in January, when Hayworth's candidacy was still embryonic, the state party opted for a closed primary, on the sound principle that party members -- there are 1.12 million registered -- should pick those who represent the party. The U.S. Supreme Court has held that the First Amendment guarantee of freedom of association, which "plainly presupposes a freedom not to associate," broadly protects parties' rights to define their identities by controlling their nominating processes.

McCain understandably wants the primary open to non-Republicans: A closed primary would favor Hayworth, many of whose supporters are the sort of high-octane conservatives who will vote in an Arizona August. Two of conservatism's current pinups -- Sarah Palin, on whom McCain conferred celebrity, and Massachusetts Sen. Scott Brown -- have campaigned here for McCain. On the other hand, Dick Armey, who is as close as the tea party movement has to a leader, denies reports that he has endorsed McCain. Arizona Rep. Jeff Flake, perhaps Congress' foremost foe of earmarks, faults Hayworth as insufficiently frugal. Hayworth endorsed and McCain opposed George W. Bush's unfunded $395 billion prescription drug entitlement. Hayworth is supported by Joe Arpaio, Maricopa County's showboating sheriff, a scourge of illegal immigrants.

Some Arizona and national Republicans worry that nominating Hayworth would exacerbate the party's problems with Hispanics, the nation's largest and fastest-growing minority. Barack Obama won 75 percent of the immigrant Latino vote in 2008. Hayworth counters, "Beware the myth of the monolith." He says "some of my most passionate support" comes from Hispanics offended by illegal immigrants.

Voters incandescent about illegal immigration might be numerous enough to decide a primary. Some seasoned Arizona Republicans say, however, that such immigration has slowed as America's economy has slowed. And they say the issue has lost some saliency here, and Arizona's economy has suffered, as some Hispanics have moved to more hospitable states. Furthermore, Hayworth may not understand Arizona's complex relationship to its centuries-old Hispanic dimension.

Democrats, having assumed that McCain will be nominated, have not groomed a top-tier opponent for him. They probably will find one if they think Hayworth can be nominated. As for the McCain-Hayworth contest, a wise Arizona Republican officeholder who is too prudent to abandon anonymity says each combustible candidate "has it in his power to lose."